The present invention relates to a head construction for a dot printer of the mechanical type using electromagnets.
A wide variety of constructions have been used for the heads of mechanical-type dot printers. Conventionally, a moving piece which has been termed an attracted iron piece comprises a moving iron core coupled so that it is attached to or free to turn on moving plates, where the core is attracted by an activated electromagnet. When moved by said electromagnet, a needle engages with the moving piece to be thrust outwardly.
Many constructions of this type have recently been disclosed. However, such constructions suffer from the difficulty that the variation in the gap between the moving iron core and the attracting surface of the electromagnet cannot be decreased without incurring a substantial increase in the cost of manufacture. Accordingly, manufacturing processes have been employed which, although providing high accuracy, require very complex adjustment of the gap, the steps involved causing a substantial increase in the cost of the head. Conversely, where an attempt has been made to lower the cost of manufacture, the variation in the gap has been increased so that where the purpose is improvement in the quality of the print effected by the device, the energy required for printing has been increased. The present invention is designed to overcome these difficulties.